two to a bed-ridden father of a large family, to save his bed and bed-clothes from being sold at the Cross.

Shepherd. But you maunna be angry at him-unless he's impidentand duns you for your donation. That's hard to thole.

Tickler. Yet, am I to apologize to him-uninformed, or misinformed, as he is about me and mine-for not drawing my purse-strings at his solicitation ? Am I to explain how it happens that I cannot comply-to tell him that, in fact, I am at that moment poor? He is not entitled to hold such a colloquy with me-yet, if I simply say, "Sir, I must refuse your petition," he probably condemns me as a heartless hunks-an unmerciful miser-and, among his friends, does not abstain from hints on my selfish character.

Shepherd. There's, for the maist part, I am willing to believe, a spice o' goodness about the greater number even o' the gadders about wi' subscription papers.

Tickler. But a spice, James, is not enough. Their motives are of too mixed a kind. Vanity, idleness, mere desire to escape ennui, curiosity even, and a habit of busy-bodyism, which is apt to grow on persons who have no very strong ties of affection binding them to home, do sadly impair the beauty of beneficence.

Shepherd. They do that-yet in a great populous city like Embro', much good must often be done by charitable people formin' themselves into associations-findin' out the deserving poor, gettin' siller subscribed for them, visitin' them in their ain houses, especially in the winter time, sir, gein' them a cart o' coals, or a pair o' blankets, or some worsted stockens, and so on-for a sma' thing is aften a great help to them just hangin' on the edge o' want; and a meal o' meat set afore a hungry family, wha hadna expeckit to break their fast that day, not only fills their stamacks, puir sowls, but warms their verra hearts, banishin' despair, as by a God-gift, and awaukenin' Hope, that had ex

pired alang wi' the last spark on the ashy hearth.

Tickler.-Give me your hand, James. James, your health-God bless you-certainly a young lady—or a middle-aged one either-never looks better-so well-as when in prudence and meekness she seeks to cheer with charity the hovels of the poor. I know several such-and though they may too often be cheated and imposed onthat is not their fault-and the discharge of a Christian duty cannot fail of being accompanied by a great overbalance of good.

Shepherd.-Oh man! Mr. Tickler but you hae a maist pleasant face the noo-you're a real gude creturand I wad fling a glass o' het water in the face o' onybody that wad daur to speak ill o' a single letter in your name.-Is't no time, think ye, sir, to be ringin' for the eisters ?—I hear them comin'!-That cretur Awmrose has the gift o' divination!

North.-Tickler puts all his soul, James, into whatever he happens to be doing at the time. Why, he brushes his hat, before turning out at two for a constitutional walk, with as much seeming, nay, real earnestness, as Barry Cornwall polishes a dramatic scene, before making an appeal to posterity.

Shepherd. aff the nap.

And baith o' them rub Commend me to a rouch hat and a rouch poem-a smooth hat's shabby-genteel, and a smooth poem's no muckle better. I like the woo on the ane to show shadows to the breeze

and the lines o' the ither to wanton like waves on the sea, that, even at the very cawmest, breaks out every noo and then into little foam-furrows, characteristic o' the essential and the eternal difference atween the waters o' an inland loch, and them o' the earth-girdlin' ocean.

tite

Tickler. I have lost my appe

Shepherd. I howp nae puir man 'Il find it, now that wages is low and wark scarce.

form the network; and so intimate is their union, and so imperceptibly do the veins assume their venous character, that it would be difficult to say where the artery ends, and the vein begins. This beautiful system of minute vessels is distributed throughout every part of the body but the skin; the various membranes, and the muscles, are supplied the most abundantly. It is not, however, into all the capillary vessels, in a natural state, that the red particles of the blood are admitted; as for instance the cornea of the eye, whose vessels contain the serous, or uncolored, portion only. This may arise from the calibre of the vessels being too minute to admit the entrance of the red particles, or, from a natural disposition and power in them, to refuse that part of the blood which would interfere with the necessary function of the organ.

As it is the office of the arteries to convey the blood from the heart to every part of the system, for its support and nourishment, so it is the office of the veins to return it to the same source, its important task being accomplished. All the veins of the body, except those of the heart itself, terminate ultimately in the two venæ cavæ, from whence the blood passes into the right auricle; this reservoir being filled, its sides immediately contract, and the blood is forced through the ostium venosum into the right ventricle, being prevented from returning back into the veins by the valve placed at their entrance into the auricle. The right ventricle, on receiving the blood, now in its turn contracts, and forces it into the pulmonary artery, by which it is carried immediately to the lungs, where, undergoing certain changes, it becomes fitted for the purposes of the animal economy. On the contraction of the ventricle, it would be natural to expect that the blood would, at least in part, return back into the auricle, and this would certainly occur, were it not prevented by the valve at the ostium venosum, or entrance into the ventricle; the same remark holds good, with respect to

the valves also on the other side of the heart.

The blood having traversed the lungs, is returned by the pulmonary veins to the left auricle of the heart; and this contracting, it is propelled into the left ventricle, from whence it is sent through the aorta and its ramifications to every part of the body; and is again returned by the veins to the right auricle. It appears, therefore, that the blood on the right side of the heart must pass through the lungs before it can be admitted into the left, in order to be conveyed by the means of arteries through the system.

Now, we shall find, upon examination, that a manifest difference exists between the blood in the veins, and in the arteries,—or, in the right, and in the left cavities of the heart; that of the veins of the right side of the heart being of a dark livid color, while its hue in the arteries and left side is scarlet or bright red. This circumstance, independent of others, indicates a change in its nature, and it is evident also, that this change must be effected in the lungs. But before proceeding, it may be proper to give a brief description of these organs, by which some idea of their structure and use may be formed.

The lungs are situated in the cavity of the chest, which when distended with air, they completely fill; their texture is light and spongy, and consists of an assemblage of most minute and numberless cells, connected together, and communicating with each other; the whole being covered by an extremely fine membrane termed the pleura. In these cells the ramifications of the trachea or wind-pipe terminate, and it is in these that the blood undergoes its change. The lungs are abundantly supplied with absorbents, and also with a considerable number of nerves, although at the same time their sensibility is very imperfect. On each dilatation of the chest there enters into these organs, according to some physiologists, between thirty and forty cubic inches, or,

at a deep inspiration, from six to eight quarts of atmospheric air, consisting, when pure, of 73 of azote or nitrogen, 27 of oxygen, and one or two parts in the 100, of carbonic acid. The character of the air, when expired, is found to be considerably altered, the portion of carbonic acid being much increased, that of the oxygen diminished, and the azote remaining apparently unchanged.

Now, on the air-cells of the lungs, the contexture of which is estimated by Håller at the 1000th part of an inch in thickness, the extreme ramifications or capillaries of the pulmonary artery are spread like a delicate network; and under such circumstances it appears, that the oxygen of the atmosphere is fully capable of acting on the blood, and affecting the requisite changes, by which, having become arterial, it is returned through the pulmonary veins, to the left side of the heart. We may here remark, that the pulmonary artery is the only artery which carries dark, or, as it is commonly called, venous blood, and it arises from one of the right cavities of the heart; while the pulmonary veins proceeding to the left are the only veins that carry arterial blood thus the blood in the right cavities of the heart is dark-colored, or venous; that in the left, bright red, or arterial.

With the passage of this fluid through the lungs is connected that most important phenomenon, the nourishment and support of the body. It is remarkable that arterial blood seems to be alone calculated to sustain the natural integrity of the animal frame; its decay and losses being repaired, and its various secretions being furnished, from arterial blood. To this rule there is however one exception, viz. the bile; this fluid is secreted by the liver from venous blood.

In venous blood is contained a large portion of carbon, acquired during its course through the animal system. Now, when it reaches the lungs, and becomes acted upon by the atmospheric air, which I have already said to be comprised principally of

oxygen and azote, the oxygen unites with a great portion of the carbon, forming carbonic acid, and is expired with the azote, which seems to be unchanged, and also with the remainder of the oxygen which exists after the production of the acid. The blood now becomes of a florid color, having parted with the carbon, to which its previous darkness was owing; and this is supposed to be the only change it undergoes during respiration. It has been, however, the opinion of several physiologists, that a part of the oxygen was absorbed by the blood, and so entered into combination with it. This again is contradicted, and with reason, as it is ascertained by experiments that the portion of oxygen which disappears, is just sufficient for the formation of the carbonic acid which is produced.

The quantity of oxygen consumed by animals in a given time is variable, not only as it regards species and individuals, but the same individual under different circumstances.

In man, the quantity of oxygen consumed in a minute has been differently rated. Allen and Pepys found it to be 26.6 cubic inches in a minute; Davy 31.6; and Murray 36. Various states of the system, however, occasion considerable differences. For instance, the quantity of oxygen consumed, is increased by exercise; and if the experiments of Peguin may be trusted, this consumption is nearly four times more than in the usual state of the body. But Prout, who has paid much attention to the subject, concluded from numberless experiments, that exercise, when moderate, increased the consumption of oxygen, but when continued so as to induce fatigue, diminished it. The exhilarating passions appear to increase the quantity; the depressing passions, on the other hand, and sleep, alcohol, and tea, to diminish the quantity. The experiments of Dr. Prout tend also to prove, that the quantity of oxygen consumed is not uniform during the twenty-four hours, but is always greater at one and the same part of

the day than at any other. For instance, that its maximum occurs between 10 A. M. and 2 P. M., or generally between 11 A. M. and 1 P. M., and that its minimum commences about Sh. 30′ P. M., and continues nearly uniform till about 3h. 30' A. M. To account for this phenomenon, Dr. P. refers, and with much probability, to the sun, as regulating by its presence or absence these variations. And we may here observe that in all diurnal animals, the season of their greatest activity is the forenoon, at which time also the consumption of the oxygen is greatest, while lassitude and fatigue come on gradually in the afternoon, when the consumption of oxygen is diminished. There are,

however, many animals from whose natural habits of activity in the night, and repose during the day, we may conclude that with them the arrangement is reversed.

From the experiments of Dr. Crawford, it would appear, that temperature exerts much influence also, as to the quantity of oxygen consumed.

He found, for example, that a guinea-pig confined in air at the temperature of 55 deg., consumed double the quantity which it did when confined in air at 104 deg.; and also that in such cases of exposure to high temperature, the venous blood had not its usual dark character, but, by its arterial florid hue, indicated that in its course through the system the natural and usual changes in it had not taken place.

When the temperature of warmblooded animals is greatly increased, exertion becomes laborious, and fatigue and lassitude, as if resulting from violent muscular efforts, are speedily induced; but, on the contrary, in cold-blooded animals, on whose system temperature has so marked an influence, that when cooled below a certain degree they become torpid, the effect of a moderate degree of heat will be to increase muscular action, and a corresponding consumption of oxygen. As the it appears that an increase of muscular ac

tion (to a certain point at least) is accompanied by an increased consumption of oxygen; so, on the other hand, as fatigue follows exertion, this increased consumption will always be succeeded by an equally great decrease, and this is indicated by yawning and drowsiness, which are also the signs of muscular exhaustion.

The amount of oxygen consumed is an index of the quantity of carbon thrown out of the system, and this in man amounts to nearly half an ounce every hour; but its relative proportion to the quantity of food taken into the system, or to the bulk or natural habits of the animal, is yet undetermined by experiments.

The blood having thus become aërated, or, to speak more correctly, deprived of the carbon which it had acquired in its course through the frame, is now fitted for the purposes of the animal economy; and it is in the order of our plan to take a closer view of the agents appointed to this end. Our readers need not now be told that these are the heart, the arteries, and the veins. The general anatomy of the heart has already been explained; it now remains for us to consider its peculiar mode of action.

We have stated this organ to be a muscle containing four cavities, destined for receiving and expelling the blood; but with respect to its action, it differs from every other in the animal frame. To other muscles, rest from their labors is necessary, that their powers of exertion may be renewed; they are wearied with toil, and require repose; those even by which respiration is effected, are refreshed at each interval. But the heart alone is unwearied; it continues its labor for years; it requires no repose; death alone puts a period to its exertions; and even then life lingers there the latest, and slowly and unwillingly retires. The heart, we have said to consist of two auricles and two ventricles, and their contraction separately on the blood has been mentioned, but it must not be thence concluded, that each of these divisions